Thursday, November 20, 2014

JSON to HashMap - Parsing JSON String

Recursivey Parsing JSON String to HashMap


Json String can contain JsonArray, JsonObject etc.

package com.test;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.codehaus.jettison.json.JSONArray;
import org.codehaus.jettison.json.JSONObject;

public class TestJson{

    public static void main(String args[]) throws Exception {
        JSONObject jsonObject = new JSONObject(
                "{\"A\":\"M1\",\"Data\":[ {\"B\":[{ \"B1\":\"111\",\"B2\":\"Warning \"},{ \"B1\":\"222\",\"B2\":\"Warning \"}],\"C\":[{\"c1\":\"IL2\",\"c2\":\"[0.750183,0.00933380975964486]\"},{\"c1\":\"IL1b\",\"c2\":\"[0.750183,-1.5216938335421]\"}]}]}");
        System.out.println(getMap(jsonObject));
    }

    private static Map getMap(JSONObject object) {
        Map<String, Object> map = new HashMap<String, Object>();

        Object jsonObject = null;
        String key = null;
        Object value = null;

        try {
            Iterator<String> keys = object.keys();
            while (keys.hasNext()) {

                key = null;
                value = null;

                key = keys.next();

                if (null != key && !object.isNull(key)) {
                    value = object.get(key);
                }

                if (value instanceof JSONObject) {
                    map.put(key, getMap((JSONObject) value));
                    continue;
                }

                if (value instanceof JSONArray) {
                    JSONArray array = ((JSONArray) value);
                    List list = new ArrayList();
                    for (int i = 0 ; i < array.length() ; i++) {
                        jsonObject = array.get(i);
                        if (jsonObject instanceof JSONObject) {
                            list.add(getMap((JSONObject) jsonObject));
                        } else {
                            list.add(jsonObject);
                        }
                    }
                    map.put(key, list);
                    continue;
                }

                map.put(key, value);
            }
        } catch (Exception e) {
            System.out.println(e);
        }
        return map;
    }
}


How to avoid extra POJO's / Classes

package com.package;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.type.TypeFactory;

public class Test{

    public static void main(String[] args) {

        String json = "[{\"givenName\": \"Adrienne H.\",\"surname\": \"Kovacs\"},{\"givenName\": \"Philip\",\"surname\": \"Moons\"}]";
        ObjectMapper mapper = new ObjectMapper();
        List<Author> list = new ArrayList<Author>();
        try {
            list = mapper.readValue(json, TypeFactory.defaultInstance().constructCollectionType(List.class, Author.class));
        } catch (JsonParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JsonMappingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        System.out.println(list);
    }
}
 
So here i do not need to map List<Author> inside any other class.